Free Float
Free Float, or Free Slack, is the gap between when a task finishes at the earliest and when its successors can start at the earliest — calculated as the earliest of the successors' Early Start Dates less the task's own Early Finish Date, measured on the Working Calendar. Relationships other than Finish-to-Start, and any lead or lag, shift the result. If the task has no successors, the project finish date is used instead. It's a more conservative measure than Total Float, since it looks only at the immediate successors rather than the whole remaining path. Scheduling tools differ only in the label they use — Microsoft Project reports this field as Free Slack, while others call it Free Float.
Why it matters
Free Float tells a scheduler how much a task can slip without creating any ripple effect on the next task at all. That's useful for avoiding disruption to other teams' start dates, even when the overall project finish date has more cushion available through Total Float.
FAQ
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